#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vl vector<ll>
#define pb push_back
#define pll pair<ll, ll>
#define vs vector<string>
#define vb vector<bool>
#define all(aaa) aaa.begin(), aaa.end()
#define rall(aaa) aaa.rbegin(), aaa.rend()
#define ff(aa, bb, cc) for(ll aa = bb; aa < cc; aa++)
#define IO ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define ed "\n"
#define fi first
#define se second
ll MOD = 1e9+7;
int main(){
ll n, m, k;
cin >> n >> m >> k;
vl arr(m);
ll suma = 0;
ff(i, 0, n){
ll x;
cin >> x;
suma += x;
}
ff(i, 0, m){
cin >> arr[i];
}
vb dp(1e6);
dp[0] = 1;
ff(i, 0, m){
for(ll j = 1e6-1; j >= 0; j--){
if(dp[j] == 1 && j+arr[i] < 1e6){
dp[j+arr[i]] = 1;
}
}
}
ll x = LLONG_MIN;
ff(i, suma, 1e6){
if(dp[i] == 1){
x = i-suma;
}
}
if(x < 0){
cout << "Impossible";
}
else{
cout << x;
}
return 0;
}
